1. Field of the Invention
This invention pertains to a system for locating a partial break or damage in a wire loop antenna such as those used in animal containment systems.
2. Description of the Related Art
Conventional animal containment systems, represented by the one illustrated at FIG. 1, include a transmitter 02, a wire loop antenna 04, and a receiver 06. Each end of the antenna 04 is in electrical communication with the transmitter 02, and the receiver 06 is carried by an animal. The transmitter 02 drives an activation signal through the antenna 04 such that the signal radiates therefrom. The receiver 06 is responsive to the activation signal such that when the animal approaches the antenna 04, the receiver 06 detects the activation signal and, in response such detection, delivers a stimulus to the animal. Typically, the wire loop antenna 04 is buried approximately two to three inches underground to maintain the antenna 04 at its desired position, to protect the antenna 04 from damage, and to hide the typically aesthetically unpleasing antenna from sight. Despite being buried, the antenna 04 is still susceptible to damage, including breaks and partial breaks. When damage does occur, the antenna 04 does not properly radiate the activation signal, and, as a result, the animal containment system does not function as designed. Accordingly, when the antenna 04 becomes damaged, the damaged section must be located, and the antenna 04 must be repaired. However, because the antenna 04 is buried underground, the location of the damaged section is not conspicuous.
Prior art includes conventional wire break location systems for locating a break in a wire loop antenna. Typically, these conventional systems include a signal transmitter and a locator. One such system is disclosed in U.S. Pat. No. 6,215,314. When there is a break in the antenna, the antenna defines two independent sections, each being electrically connected to the transmitter of the animal containment system. Each section of the broken antenna is disconnected from the transmitter of the animal containment system and is connected to the signal transmitter of the break location system. The signal transmitter transmits a first continuous wave signal at a first frequency through one section of the antenna and transmits a second continuous wave signal at a second frequency through the other section. The first frequency is different from the second frequency such that the first continuous wave signal is distinguishable from the second continuous wave signal.
The locator receives the continuous wave signals such that when the first continuous wave signal is received, the locator generates a first continuous audible tone, and when the second continuous wave signal is received, the locator generates a second continuous audible tone. Each audible tone reflects the frequency at which its corresponding continuous wave signal is transmitted such that each audible tone is distinguishable by way of its pitch. As the first and second continuous wave signals are being transmitted through the respective sections of the antenna, the locator is carried in proximity to and along the antenna, starting at one end thereof. For example, initially, the locator is carried along the section of the antenna through which the first continuous wave signal is transmitted. While being carried along this section, the locator generates the first continuous audible tone, indicating its reception of the first continuous wave signal. After the locator traverses the break in the antenna, it is no longer proximate the section of the antenna through which the first continuous wave signal is transmitted but is proximate the section of the antenna through which the second continuous wave signal is transmitted. Consequently, as the locator traverses the break, it shifts from generating the first continuous audible tone to generating the second continuous audible tone. Accordingly, the user determines that the break in the antenna is proximate the location of the locator when the locator shifts from generating the first continuous audible tone to generating the second continuous audible tone.
Conventional wire break location systems are limited in that they are largely ineffective in detecting and locating partial breaks or other damage less than a complete break in a wire loop antenna. More specifically, when the damage to the antenna is not a complete break, the locator does not detect an abrupt change in the transmitted signal at the location of the damage because the first continuous wave signal and the second continuous wave signal are radiated not just from their respective sections of the antenna, but from the entire antenna. Because the attenuation of each of the signals is more gradual, the portion of the antenna where the locator detects both the first continuous wave signal and the second continuous wave signal is extensive. Additionally, because the distinguishing feature of the continuous wave signals is the transmission frequency and because the respective audible tones merely reflect the transmission frequencies, the user is unable to determine the transition from the first continuous audible tone to the second continuous audible tone and, thus, unable to determine the location of the damage to the antenna within a reasonable spatial range. Consequently, a device that indicates the location of a partial break or other damage less than a complete break in a wire loop antenna is desired.